Protein changes in aging and cataractous lenses may be due to the activity of proteolytic enzymes. Normal and cataractous rat and human lens crystallins have been fractionated and characterized in this laboratory. Decreases in the amounts of proteins, changes in the state of aggregation and shifts in the relative levels of the crystallin fractions have been observed. The bovine lens neutral proteinase has been prepared and a study of its specificity undertaken using alpha2-crystallin as a substrate. We propose to further purify this enzyme and characterize its activity, substrates and products. In addition, we plan to study the neutral proteinase in normal and galactose-induced cataractous rat lenses and then use our positive findings and techniques to determine the involvement of the neutral proteinase in human cataractogenesis.